Automatic container filling machines commonly available in the industry utilize positive displacement pumps to sequentially deliver precise amounts of liquid. The pump assembly has an elongated cylindrical casing that receives a reciprocating plunger. During the pump fill stroke the plunger is displaced in the elongated casing to increase the void volume of the pump chamber and thus cause liquid to be admitted therein through an inlet port. To discharge the liquid, the direction of travel of the plunger is reversed. The liquid is expelled through an outlet port that is in fluid communication with the dispensing nozzle delivering the liquid to a bottle to be filled. Suitable check valves are provided in the inlet and the outlet ports to control the direction of liquid flow in accordance with the movement of the plunger.
An automatic filling machine commercialized by Capmatic Ltd., Montreal, Canada, under the brand name PATRIOT is an example of a sequential liquid dispensing device utilizing a bank of positive displacement pumps that are capable of filling several containers during each liquid dispensing cycle. Each pump is operated by a rotary actuator connected to the reciprocating plunger. The distance between the rotation axis of the actuator and the plunger extremity determines the pump stroke, hence the amount of liquid delivered by the pump. A precise micrometric screw allows to vary the distance at which the plunger is located with relation to the rotation axis of the actuator for making volume changes.
The drawback of this approach is the requirement to manually operate the micrometric screw for making the desired volume adjustments. Thus, the filling machine must be stopped every time changes to the dispensed volume are required. Such changes are performed between production runs when the filling machine is adjusted to process containers of different size. In other instances, small volume changes may need to be performed during a production run, particularly to fine tune the amount of liquid delivered at each dispensing cycle. With the prior art arrangement described above, the technician may need to stop the entire liquid packaging line several times until the precise volume setting has been found by trial and error. This may result in a significant amount of lost production.